* Allow render function to return undefined to skip the file write.

* `compileOptions: permalink: false` now aliases to `compileOptions: permalink: () => false`. Use `compileOptions: permalink: "raw"` to skip permalink compilation altogether

src/Engines/Custom.js

@@ -186,9 +186,15 @@ class CustomEngine extends TemplateEngine {
   permalinkNeedsCompilation(str) {
     if (this.entry.compileOptions && "permalink" in this.entry.compileOptions) {
       let p = this.entry.compileOptions.permalink;
-      if (p === false || p === "raw") {
+      if (p === "raw") {
         return false;
       }
+
+      // permalink: false is aliased to permalink: () => false
+      if (p === false) {
+        return () => false;
+      }
+
       return this.entry.compileOptions.permalink;
     }
 

src/Template.js

@@ -492,6 +492,7 @@ class Template extends TemplateContent {
     return ret;
   }
 
+  // Used only by tests
   async renderContent(str, data, bypassMarkdown) {
     return super.render(str, data, bypassMarkdown);
   }
@@ -678,11 +679,18 @@ class Template extends TemplateContent {
           date: data.page.date,
           outputPath: data.page.outputPath,
           url: data.page.url,
+          checkTemplateContent: true,
           set templateContent(content) {
+            if (content === undefined) {
+              this.checkTemplateContent = false;
+            }
             this._templateContent = content;
           },
           get templateContent() {
-            if (this._templateContent === undefined) {
+            if (
+              this.checkTemplateContent &&
+              this._templateContent === undefined
+            ) {
               if (this.template.behavior.isRenderable()) {
                 // should at least warn here
                 throw new TemplateContentPrematureUseError(
@@ -728,11 +736,18 @@ class Template extends TemplateContent {
             pageNumber: pageNumber,
             outputPath: pageData.page.outputPath,
             url: pageData.page.url,
+            checkTemplateContent: true,
             set templateContent(content) {
+              if (content === undefined) {
+                this.checkTemplateContent = false;
+              }
               this._templateContent = content;
             },
             get templateContent() {
-              if (this._templateContent === undefined) {
+              if (
+                this.checkTemplateContent &&
+                this._templateContent === undefined
+              ) {
                 if (this.template.behavior.isRenderable()) {
                   throw new TemplateContentPrematureUseError(
                     `Tried to use templateContent too early (${this.inputPath} page ${this.pageNumber})`
@@ -803,13 +818,9 @@ class Template extends TemplateContent {
         await mkdir(templateOutputDir, { recursive: true });
       }
 
-      if (Buffer.isBuffer(finalContent)) {
-        finalContent = finalContent.toString();
-      }
-
-      if (typeof finalContent !== "string") {
+      if (!Buffer.isBuffer(finalContent) && typeof finalContent !== "string") {
         throw new Error(
-          `The return value from the render function for the ${this.engine.name} template was not a string. Received ${finalContent}`
+          `The return value from the render function for the ${this.engine.name} template was not a String or Buffer. Received ${finalContent}`
         );
       }
 
@@ -854,7 +865,6 @@ class Template extends TemplateContent {
     return Promise.all(
       mapEntry._pages.map(async (page) => {
         let content;
-
         // Note that behavior.render is overridden when using json or ndjson output
         if (mapEntry.template.behavior.isRenderable()) {
           // this reuses page.templateContent, it doesn’t render it
@@ -907,7 +917,10 @@ class Template extends TemplateContent {
           return;
         }
 
-        return this._write(page.outputPath, content);
+        // compile returned undefined
+        if (content !== undefined) {
+          return this._write(page.outputPath, content);
+        }
       })
     );
   }

src/TemplateContent.js

@@ -344,6 +344,7 @@ class TemplateContent {
     // No string compilation:
     //    ({ compileOptions: { permalink: "raw" }})
     // These mean `permalink: false`, which is no file system writing:
+    //    ({ compileOptions: { permalink: false }})
     //    ({ compileOptions: { permalink: () => false }})
     //    ({ compileOptions: { permalink: () => (() = > false) }})
     if (permalinkCompilation === false) {

src/TemplateMap.js

@@ -603,7 +603,10 @@ class TemplateMap {
         // This check skips precompiled collections
         if (entry) {
           let index = item.pageNumber || 0;
-          item.templateContent = entry._pages[index]._templateContent;
+          let content = entry._pages[index]._templateContent;
+          if (content !== undefined) {
+            item.templateContent = content;
+          }
         }
       }
     }

test/TemplateTest-CompileOptions.js

@@ -47,7 +47,7 @@ test("Custom extension (.txt) with custom permalink compile function", async (t)
   });
 });
 
-test("Custom extension with and opt-out of permalink compilation", async (t) => {
+test("Custom extension with and compileOptions.permalink = false", async (t) => {
   let eleventyConfig = new TemplateConfig();
   eleventyConfig.userConfig.extensionMap.add({
     extension: "txt",
@@ -73,6 +73,41 @@ test("Custom extension with and opt-out of permalink compilation", async (t) =>
     eleventyConfig
   );
 
+  let data = await tmpl.getData();
+  t.is(await tmpl.render(data), "Sample content");
+  t.deepEqual(await tmpl.getOutputLocations(data), {
+    href: false,
+    path: false,
+    rawPath: false,
+  });
+});
+
+test("Custom extension with and opt-out of permalink compilation", async (t) => {
+  let eleventyConfig = new TemplateConfig();
+  eleventyConfig.userConfig.extensionMap.add({
+    extension: "txt",
+    key: "txt",
+    compileOptions: {
+      permalink: "raw",
+    },
+    compile: function (str, inputPath) {
+      // plaintext
+      return function (data) {
+        return str;
+      };
+    },
+  });
+
+  let dataObj = new TemplateData("./test/stubs/", eleventyConfig);
+  let tmpl = getNewTemplate(
+    "./test/stubs/custom-extension.txt",
+    "./test/stubs/",
+    "dist",
+    dataObj,
+    null,
+    eleventyConfig
+  );
+
   let data = await tmpl.getData();
   t.is(await tmpl.render(data), "Sample content");
   t.deepEqual(await tmpl.getOutputLocations(data), {
@@ -206,3 +241,35 @@ test("Custom extension (.txt) with custom permalink compile function that return
     rawPath: false,
   });
 });
+
+test("Custom extension (.txt) that returns undefined from compile", async (t) => {
+  let eleventyConfig = new TemplateConfig();
+  eleventyConfig.userConfig.extensionMap.add({
+    extension: "txt",
+    key: "txt",
+    compile: function (str, inputPath) {
+      t.is(str, "Sample content");
+      return function (data) {
+        return undefined;
+      };
+    },
+  });
+
+  let dataObj = new TemplateData("./test/stubs/", eleventyConfig);
+  let tmpl = getNewTemplate(
+    "./test/stubs/custom-extension-no-permalink.txt",
+    "./test/stubs/",
+    "dist",
+    dataObj,
+    null,
+    eleventyConfig
+  );
+
+  let data = await tmpl.getData();
+  t.is(await tmpl.render(data), undefined);
+  let pages = await tmpl.getTemplates(data);
+  for (let page of pages) {
+    page.templateContent = undefined;
+    t.is(page.templateContent, undefined); // shouldn’t throw an error
+  }
+});